Heavyweight contender Tomasz Adamek got a new opponent for his fight next month when Tony Grano withdrew Thursday night because of an injury and was replaced a couple of hours later by Dominick Guinn.

Adamek, a former cruiserweight and light heavyweight titleholder, was scheduled to meet Grano in a 10-round bout on a "Fight Night" tripleheader Aug. 3 (NBC Sports Network) at the Mohegan Sun resort in Uncasville, Conn. However, Grano (20-3-1, 16 KOs), 32, of Hartford, Conn., was diagnosed with two herniated disks in his neck and was forced to pull out of the bout, Main Events matchmaker Jolene Mizzone told ESPN.com.

"He said his neck was bothering him for two weeks and he went to get the MRI [on Wednesday] and he got the results [Thursday], and the doctor said there's no way he could fight, because it was hitting his spinal cord," Mizzone said.

Mizzone put the word out to various heavyweights in a search for a replacement, and Guinn, once promoted by Main Events, accepted the fight less than an hour later.

"Dominick had called me about a week and a half ago and was saying, 'If there's anything, I'm available to fight.' I asked him if he was in the gym and he said he was and I told him I don't have anything now but stay in the gym because I have a heavyweight fight on Aug. 3, so who knows if something might happen," Mizzone said. "I called him after I heard about Grano and told Dominick this is an opportunity. He said, 'Let me talk to my coach.' He got back to me in about a half-hour. It just worked out."

Poland's Adamek (48-2, 29 KOs), 36, who lives in Jersey City, N.J., has won four consecutive fights. However, he is coming off a highly controversial split-decision victory against former cruiserweight titlist Steve Cunningham in their December rematch.

Guinn (34-9-1, 23 KOs), 38, of Hot Springs, Ark., was once one of the top-rising American heavyweight contenders. But an upset split-decision loss to former title challenger Monte Barrett in 2004 began a 1-3-1 rut that Guinn never has recovered from as he went from contender to stepping-stone journeyman.

Still, he is very experienced, having faced opponents such as James Toney, Audley Harrison (a win), Tony Thompson, Eddie Chambers and Kubrat Pulev. Guinn has not fought since June 2012, when he ended a three-fight losing streak by scoring a first-round knockout of Stacy Frazier.

The Aug. 3 card also features Brooklyn, N.Y., middleweight Curtis Stevens (24-3, 17 KOs), who recently dropped down in weight from super middleweight, against Saul Roman (37-9, 31 KOs) of Mexico in a scheduled 10-rounder in the main event.

Philadelphia's Chambers (36-3, 18 KOs), a longtime heavyweight contender who suffered a decision loss to Adamek last June, is also on the card. He is moving down in weight to cruiserweight and will face southpaw Thabiso Mchunu (13-1, 10 KOs), who will be fighting outside his native South Africa for the first time.